Semiconductor integrated circuit

ABSTRACT

A discriminating method for a trimming error is provided. A fuse is connected between an output terminal and a terminal having a potential at a VDD or VSS level, and an output voltage at the time of the trimming error is fixed. Alternatively, when the trimming error occurs, short circuit is established between VDD and VSS, and a large current is made to flow, thereby making error detection easy.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a semiconductor integrated circuit for discriminating trimming failure.

[0003] 2. Description of the Related Art

[0004] An example of conventional trimming is shown in FIG. 8. The conventional trimming is then described. In FIG. 8, the resistance between a terminal 811 and a negative power supply VSS corresponds to a resistance 841 by cutting a fuse 821. Further, if the fuse 821 is not cut, the resistance between the terminal 811 and the negative power supply VSS corresponds to a combined resistance of the resistance 841 and a resistance 842. A voltage of the terminal 811 of the circuit in FIG. 8 is controlled by the resistance ratio to a resistance 843.

[0005] In the conventional trimming, a non-conforming article is generally provided if trimming is not performed. However, there is a possibility that a conforming article is provided without performing trimming depending on a range of an efficiency voltage of a test. In this case, even if laser is radiated to the position off the fuse so that trimming fails to be performed because of positional deviation of trimming alignment, or the like, the conforming article may be provided at the time of the test. In addition, there is a fear that the radiation of laser to the wrong position affects long-term reliability, and thus, the non-conforming article has to be correctly discriminated.

SUMMARY OF THE INVENTION

[0006] In order to solve the above-described problems, an object of the present invention is to provide a semiconductor integrated circuit having a structure in which a dummy fuse is used to discriminate failure in accordance with an output thereof in the case of a trimming error. The semiconductor integrated circuit as structured above has a strong point in that success or failure of trimming can be discriminated in accordance with whether the output is fixed to VSS or VDD or not. Further, such a structure is adopted in which, if trimming is not performed, short circuit is established between positive and negative power supply voltages, whereby the success or failure of trimming can be discriminated by examining a consumption current.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In the accompanying drawings:

[0008]FIG. 1 is a structural diagram of a CMOS circuit of the present invention;

[0009]FIG. 2 is a structural diagram of a CMOS circuit of the present invention;

[0010]FIG. 3 is a structural diagram of a CMOS circuit of the present invention;

[0011]FIG. 4 is a structural diagram of a CMOS circuit of the present invention;

[0012]FIG. 5 is a structural diagram of a CMOS circuit of the present invention;

[0013]FIG. 6 is a structural diagram of a CMOS circuit of the present invention;

[0014]FIG. 7 is a structural diagram of a CMOS circuit of the present invention;

[0015]FIG. 8 shows an example of a structural diagram of a conventional trimming mechanism;

[0016]FIG. 9 is a layout example of a trimming mechanism of the present invention;

[0017]FIG. 10 is a circuit diagram of the trimming mechanism of the present invention; and

[0018]FIG. 11 is a layout example of a trimming mechanism of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIGS. 1 to 7 show examples of a structure of a CMOS circuit according to the present invention.

[0020]FIG. 1 is a diagram showing an embodiment of the present invention, in which one end of a fuse 121 is connected between an output of a CMOS circuit 100 and an output terminal 111, and another end of the fuse 121 is connected to a transistor 131. In FIG. 1, if trimming is correctly performed, the fuse 121 is cut, and a potential of the output terminal 111 is determined by the CMOS circuit 100. In the case where trimming failure occurs, when a signal is input to a test terminal 112 to make the transistor 131 conductive, the output terminal 111 is connected to a negative power supply voltage VSS via the fuse 121, and thus, the potential of the output terminal 111 becomes VSS. Therefore, a trimming error is detected.

[0021]FIG. 2 is a diagram showing another embodiment of the present invention, in which one end of a fuse 221 is connected between an output of a CMOS circuit 200 and an output terminal 211, and another end of the fuse 221 is connected to a transistor 231. In FIG. 2, if trimming is correctly performed, the fuse 221 is cut, and a potential of the output terminal 211 is determined by the CMOS circuit 200. In the case where trimming failure occurs, when a signal is input to a test terminal 212 to make the transistor 231 conductive, the output terminal 211 is connected to a positive power supply voltage VDD via the fuse 221, and thus, the potential of the output terminal 211 becomes VDD. Therefore, a trimming error is detected.

[0022]FIG. 3 is a diagram showing another embodiment of the present invention, in which a transistor 331 and a fuse 321 are connected in series between an output of a CMOS circuit 300 and an output terminal 311. In FIG. 3, if trimming is correctly performed, the fuse 321 is cut, and a potential of the output terminal 311 is determined by the CMOS circuit 300. In the case where trimming failure occurs, when a signal is input to a test terminal 312 to make the transistor 331 conductive, the output terminal 311 is connected to a negative power supply voltage VSS via the fuse 321, and thus, the potential of the output terminal 311 becomes VSS. Therefore, a trimming error is detected.

[0023]FIG. 4 is a diagram showing another embodiment of the present invention, in which a transistor 431 and a fuse 421 are connected in series between an output of a CMOS circuit 400 and an output terminal 411. In FIG. 4, if trimming is correctly performed, the fuse 421 is cut, and a potential of the output terminal 411 is determined by the CMOS circuit 400. In the case where trimming failure occurs, when a signal is input to a test terminal 412 to make the transistor 431 conductive, the output terminal 411 is connected to a positive power supply voltage VDD via the fuse 421, and thus, the potential of the output terminal 411 becomes VDD. Therefore, a trimming error is detected.

[0024] In FIG. 5, if trimming is correctly performed, a fuse 521 is cut, and a current does not flow through a transistor 531. In the case where trimming failure occurs, when a signal is input to a test terminal 512 to make the transistor 531 conductive, a through current flows. Therefore, a trimming error is detected.

[0025] In FIG. 6, if trimming is correctly performed, a fuse 621 is cut, and a current does not flow through a transistor 631. In the case where trimming failure occurs, when a signal is input to a test terminal 612 to make the transistor 631 conductive, a through current flows. Therefore, a trimming error is detected.

[0026] In FIG. 7, if trimming is correctly performed, a fuse 721 or a fuse 722 is cut, and a through current does not flow through transistors 731 and 732. In the case where trimming failure occurs, when signals are input to test terminals 712 and 713 to make the transistors 731 and 732 conductive, respectively, a through current flows. Therefore, a trimming error is detected.

[0027]FIG. 9 and FIG. 10 are a layout example and a circuit diagram corresponding thereto, respectively. In FIG. 9, laser trimming is conducted in accordance with an alignment 951. If trimming is correctly performed to main fuses 921 and 922, a fuse for error detection 923 is also necessarily cut. On the contrary, in the case where the trimming of the main fuses 921 and 922 is not correctly performed since laser trimming is not performed in accordance with the alignment because of the existence of impurities, or the like, the fuse for error detection is not cut as well. Therefore, a trimming error is detected.

[0028] Also, in the case where positional deviation occurs when a plurality of chips are aligned with one alignment as shown in FIG. 11, success or failure of trimming of the main fuse is judged by the fuse for error detection.

[0029] The present invention is implemented in accordance with the embodiment described above, and provides the following effects: the output terminal voltage is fixed to the power supply voltage when trimming failure occurs; the detection of the trimming error is facilitated by flowing a large current; and thus, the discrimination of the circuit in which trimming has not been correctly performed is enabled. 

1.-9. (canceled).
 10. A CMOS circuit, comprising: a CMOS circuit; a MOS transistor connected to the CMOS circuit and having a source terminal, a gate terminal, and a drain terminal, the source terminal being connected to a power supply voltage and the gate terminal being connected to a test signal terminal; and a fuse element having one end connected to the drain terminal and another end connected to an output terminal of the CMOS circuit.
 11. A CMOS circuit according to claim 10; wherein the power supply voltage to which the source terminal is connected is a negative power supply voltage.
 12. A CMOS circuit according to claim 10; wherein the power supply voltage to which the source terminal is connected is a positive power supply voltage.
 13. A CMOS circuit, comprising: a CMOS circuit; a MOS transistor connected to the CMOS circuit and having a source terminal, a gate terminal, and a drain terminal, the drain terminal being connected to an output terminal of the CMOS circuit and the gate terminal being connected to a test signal terminal; and a fuse element having one end connected to the source terminal and another end connected to a power supply voltage.
 14. A CMOS circuit according to claim 13; wherein the power supply voltage to which the fuse element is connected is a negative power supply voltage.
 15. A CMOS circuit according to claim 13; wherein the power supply voltage to which the fuse element is connected is a positive power supply voltage. 